This invention relates generally to trickle irrigation valve devices of a type adapted for installation through the wall of a water supply conduit, such as plastic tubing, garden hose, and the like. More particularly, this invention relates to an improved trickle irrigation unit for supplying relatively low flow rates of irrigation water through a variable selected number of outlet ports.
A wide variety of so-called trickle irrigation valve devices are known for use in supplying water at a relatively low, substantially drip flow rate to irrigate crops and the like without significant water evaporation and/or soil erosion. Such trickle irrigation devices are typically installed along the length of an elongated water supply conduit at predetermined points whereat irrigation water is desired, such as directly at the bases of individual plants, with water under pressure is being supplied through the conduit for flow into and through the trickle devices. The trickle devices are designed to discharge relatively small water flows at a substantially reduced pressure, such that the water is emitted without spraying at a low flow rate, such as on the order of about one-half gallon per hour.
In one common form, trickle irrigation devices have been provided as self-contained valve assemblies adapted for rapid mounting onto the exterior of a water supply conduit typically by means of a barbed inlet spike piercing the conduit wall. Water under pressure within the supply conduit is permitted to flow through the inlet spike into a pressure chamber having a resilient valve flap overlying a recessed flow pattern at one side of the pressure chamber. This valve flap cooperates with the recessed flow pattern to define a variable geometry flow path permitting controlled pressure-responsive water leakage to an outlet port for discharge to the exterior of the trickle irrigation unit. In many such trickle irrigation unit designs, the flow pattern is configured to permit a relatively high flushing flow to the outlet port when the pressure within the supply conduit is relatively low and to restrict water flow at comparatively higher conduit pressures to a relatively low, substantially drip rate. For one example of a trickle irrigation device of this general type, see U.S. Pat. No. 3,954,223.
Previous trickle irrigation devices have generally been limited to a single outlet port, whereby multiple trickle units have been necessary whenever a plurality of irrigation discharge flows are desired. This requirement for multiple trickle units can be disadvantageous, particularly when a plurality of discharge flows are required within a short length of the water supply conduit. For example, the short conduit span may be insufficient to accommodate the number of individual trickle units needed to provide the requisite number of discharge flows. Moreover, mounting of several closely spaced trickle units onto the supply conduit requires the formation of several closely spaced holes in the conduit wherein these holes can unduly weaken the conduit structure thereby increasing the risk of conduit failure during operation.
More recently, multiple outlet trickle irrigation devices have been proposed including a single inlet port permitting water inflow to a pressure chamber from which the water is discharged through a plurality of outlet ports. Such multiple outlet trickle devices advantageously have provided multiple discharge flows of irrigation water within a short length of the supply conduit without requiring multiple holes in the conduit wall. However, in many instances, the multiple outlet device provides discharge flows in a number which does not correspond with the number of discharge flows actually required or desired for a given application. Accordingly, with these previous multiple outlet devices, it has been necessary to provide additional components, such as closure caps and the like, for sealing off unused outlet ports. Such closure caps must be provided at additional expense and typically comprise relatively small items which can become lost or inadvertently removed from the trickle unit.
There exists, therefore, a significant need for an improved multiple outlet trickle irrigation unit having a plurality of outlet ports and further including integrated selector means for selectively and variably controlling the number of outlet ports through which irrigation water is discharged at a substantially trickle flow rate. The present invention fulfills this need and provides further related advantages.